1. Field of the Invention
The present invention relates to a waterproof camera and more particularly a lens mount of a waterproof camera for mounting a waterproof photographic lens on a camera main body.
2. Related Background Art
A lens mount for mounting a waterproof type photographic lens on a camera main body has been disclosed in U.S. Pat. No. 4,994,829. The waterproof camera with the lens mount of the type described above has been well known to those skilled in the art. The construction of such waterproof camera will be briefly described hereinafter for the sake better understanding of the present invention with reference to FIG. 3. A camera mechanism assembly 51 includes a film rewinding mechanism of a camera main body 50. The camera mechanism assembly is incorporated into an outer box 54 whose back is closed by a back plate 52. The back plate 52 is provided with an O-ring which is made into very close watertight contact with the outer box 54. A waterproof photographic lens generally indicated by the reference number 60 comprises an inner cylinder 61 and an outer cylinder 65 and the inner cylinder 61 is fitted into the outer cylinder 65 and is detachably held therein. The inner cylinder 60 is mounted on an inner mount 55 of the camera mechanism assembly 51 while the outer cylinder 65 is mounted on an outer mount 56 of the outer box 54. The outer mount 56 is attached in coaxial relationship with the inner mount 55. The inner cylinder 61 holds lens elements of the waterproof photographic lens 60 and is watertightly sealed with an O-ring 63 interposed between a waterproof glass 62 which covers the front surface of the inner cylinder on the one hand and the outer cylinder 65 on the other side and an O-ring 64 fitted into an O-ring receiving groove 65a of the outer cylinder 65. When the photographic lens 60 is mounted on the camera main body 50, the inner cylinder 61 is mounted through the inner mount 55 on the camera mechanism assembly 51. The outer cylindrical periphery 65 is mounted on the outer box 54 through the outer mount 56 which is watertightly sealed by O-ring 64. However, the waterproof camera with the above described construction has the following problems.
(1) Since various signals are exchanged through electrical contacts between the photographic lens 60 and the camera main body 50, the inner cylinder 60 of the photographic lens 60 must be correctly located at a predetermined position with respect to the camera main body 50. If the axes of the mounts 55 and 56 are offset, the signal exchanges between the electrical contacts cannot be correctly carried out so that there is a fear that the erroneous operation of the camera happens. However, from the standpoint of a degree of precision machining and errors resulting from the assembly step, it is extremely difficult to align the axis of the inner mount 55 securely attached to the camera mechanism assembly 51 incorporated in the outer box 54 with the axis the outer mount 56 on the outer box 54. The reason is that it is difficult to attach the outer mount at a predetermined position on the outer box 54 and mount the inner mount at a predetermined position on the camera mechanism assembly. Furthermore, when the camera mechanism assembly 51 is not mounted in the outer box at a predetermined position, the outer and inner mounts are not in coaxial relationship.
(2) When the photographic lens 60 is forcibly mounted even when the axis of the outer and inner mounts are not aligned with each other, both the inner and outer cylinders 61 and 65 are forcibly mounted on the inner and outer mounts 55 and 56, respectively, in offset relationship with each other. As a result, the O-ring 64 is offset from the correct sealing position so that water very frequently tends to leak into the outer box 54 from an erroneously watertightly sealed portion.
(3) In the case of mounting and dismounting of the photographic lens 60, there is a fear that the water which remains in the O-ring groove 65a tends to permeate into the interior of the outer mount 56. This water flows through the space defined between the outer and inner mounts 56 and 55 into the interior of the outer box 54 so that there exists also a fear that the corrosion of the internal components and the malfunction of the electric circuits result.